DACs generally experience output noise that can cause inaccuracy in their sigma delta modulators and input to output non-linearity, and thus require calibration. A calibration approach to improve linearity uses spectral shaping to reduce in-band noise, but is ineffective for wide band (e.g., low OSR (over sampling rate) applications). Another approach requires an extra sigma-delta modulator for efficient calibration.
Like reference symbols in the various drawings indicate like elements.